Pregnant or not?

Hi guys! So, I just got in a serious relationship and we just started having sex. Before that I hadn’t had sex for 2 or 3 months.

I’m on a daily oral birth control and we’ve been using the not so accurate pull out method.

This week is my period week(ya know the placebo pills) and for some reason my period is late. But! Wait! Here’s the kicker. I’ve taken 4 pregnancy tests which have all come back negative. So I’m here asking all you girls what you think is happening.

Is it normal for your period to be delayed on a birth control? because it’s never happened to me before.

Should I go see my doctor?

If I don’t start my period by the end of the week should I start my next pack of pills or keep waiting till the period comes?

And could this have something to do with me not having sex for awhile, because I have read that sometimes your first time or first time in a while can mess with your period(although the science behind that doesn’t seem real)